codemod is removing async from methods

Input:

```js
export default Controller.extend({
  async save() {
    await this.something;
  },
});
```

Expected Output:

```js
export default class MyController extends Controller {
  async save() {
    await this.something;
  }
}
```

Actual Output:

```js
export default class MyController extends Controller {
  save() {
    await this.something;
  }
}
```